This invention relates generally to data processing systems in an interconnected environment. More particularly, it relates to an improved method for transmitting small packets of data in a data processing system in an interconnected environment.
It is becoming increasingly prevalent to couple a plurality of data processing systems in an interconnected computing environment such as a Local Area Network (LAN) or Wide Area Network (WAN). The networks are becoming increasingly complicated, with several different LAN networks of different protocols coupled together with the data processing systems from multiple vendors in the network.
To assure that different network technologies can communicate with each other, most vendors provide capability to interface according to the IEEE and International Standard Organization's standards for Local Area Networks. ISO 8802-2 (IEEE Standard 802.2-1989) Logical Link Control Protocol describes the data link layer in a Local Area Network. ISO 8802-3 (IEEE Standard 802.3-1988) describes a bus utilizing CSMA/CD as the access method. ISO 8802-4 (IEEE Standard 802.4-1985) describes a bus utilizing token passing as the access method. ISO 8802-5 (IEEE Standard 802.5-1989) describes a ring utilizing token passing as the access method. ISO 8802-7 describes the ring utilizing a slotted ring as the access method. This family of standards deals with the physical and data link layers as defined by the ISO open systems interconnection reference model.
The data link layer described in ISO 8802-2 consists of a top or logical link control (LLC) sublayer and a bottom layer or medium access control (MAC) sublayer which is defined to complete the functionality of the data link layer to connect to the physical layer. The ISO 8802-2 standard has two LLC protocols for communication between two systems in the network to satisfy a broad range of potential applications. The ISO 8802-2 LLC type 1 protocol is a connectionless protocol with minimum protocol complexity which has no guarantee of delivery to the receiving system and is described in Section 6 of the ISO standard. This mode is useful when the higher layers, e.g., applications, provide any essential recovery and sequences so they do not need replicating in the data link layer. This type of operation also is useful in applications where it is not essential to guarantee the delivery of every data packet. The ISO 8802-2 LLC type 2 protocol is a connection-based protocol for guaranteed delivery. This mode includes support of sequence delivery of data link layer units and a comprehensive set of data link layer recovery techniques. This second type of operation is described in section 7 of the ISO standard. Because many network servers and message transfer interfaces, such as IBM's LAN Server.TM. and NetBIOS.TM., call for session-oriented data transfer between two systems on a network, to track transactions for each client, they are generally forced to use a session-level protocol and the 802.2 type 2 protocol on all data transfers. While this data transfer method can be efficient for large messages, for small messages the performance is relatively poor.